[A DRIFTS study of SO2 oxidation on the surface of CaCO3 particles].

CaCO3 is an important component of mineral dust aerosols in the atmosphere, but its role in atmospheric heterogeneous chemistry is still unclear. In this paper, the oxidation of SO2 on CaCO3 particles was studied using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Formation of sulfite and sulfate was identified on the surface, and the role of O3 on the oxidation process is determined by comparing the experiments in different conditions. DRIFTS is proved as a useful tool for studying heterogeneous reactions on CaCO3 particles. The results show that in the presence of O3, SO2 can be oxidized into sulfate on the surface of CaCO3 particles. A two-step mechanism that involves adsorption of SO2 followed by oxidation is presented.